usb: dwc3: meson-g12a: Add support for IRQ based OTG switching

Add support for the OTG ID change interrupt to switch between Host
and Device mode.

Tested on the Hardkernel Odroid-N2 board.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/dwc3/dwc3-meson-g12a.c

@@ -11,9 +11,7 @@
  * - Control registers for each USB2 Ports
  * - Control registers for the USB PHY layer
  * - SuperSpeed PHY can be enabled only if port is used
- *
- * TOFIX:
- * - Add dynamic OTG switching with ID change interrupt
+ * - Dynamic OTG switching with ID change interrupt
  */
 
 #include <linux/module.h>
@@ -348,6 +346,22 @@ static enum usb_role dwc3_meson_g12a_role_get(struct device *dev)
 		USB_ROLE_HOST : USB_ROLE_DEVICE;
 }
 
+static irqreturn_t dwc3_meson_g12a_irq_thread(int irq, void *data)
+{
+	struct dwc3_meson_g12a *priv = data;
+	enum phy_mode otg_id;
+
+	otg_id = dwc3_meson_g12a_get_id(priv);
+	if (otg_id != priv->otg_phy_mode) {
+		if (dwc3_meson_g12a_otg_mode_set(priv, otg_id))
+			dev_warn(priv->dev, "Failed to switch OTG mode\n");
+	}
+
+	regmap_update_bits(priv->regmap, USB_R5, USB_R5_ID_DIG_IRQ, 0);
+
+	return IRQ_HANDLED;
+}
+
 static struct device *dwc3_meson_g12_find_child(struct device *dev,
 						const char *compatible)
 {
@@ -374,7 +388,7 @@ static int dwc3_meson_g12a_probe(struct platform_device *pdev)
 	void __iomem *base;
 	struct resource *res;
 	enum phy_mode otg_id;
-	int ret, i;
+	int ret, i, irq;
 
 	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
 	if (!priv)
@@ -436,6 +450,19 @@ static int dwc3_meson_g12a_probe(struct platform_device *pdev)
 	/* Get dr_mode */
 	priv->otg_mode = usb_get_dr_mode(dev);
 
+	if (priv->otg_mode == USB_DR_MODE_OTG) {
+		/* Ack irq before registering */
+		regmap_update_bits(priv->regmap, USB_R5,
+				   USB_R5_ID_DIG_IRQ, 0);
+
+		irq = platform_get_irq(pdev, 0);
+		ret = devm_request_threaded_irq(&pdev->dev, irq, NULL,
+						dwc3_meson_g12a_irq_thread,
+						IRQF_ONESHOT, pdev->name, priv);
+		if (ret)
+			return ret;
+	}
+
 	dwc3_meson_g12a_usb_init(priv);
 
 	/* Init PHYs */
@@ -460,7 +487,6 @@ static int dwc3_meson_g12a_probe(struct platform_device *pdev)
 
 	/* Setup OTG mode corresponding to the ID pin */
 	if (priv->otg_mode == USB_DR_MODE_OTG) {
-		/* TOFIX Handle ID mode toggling via IRQ */
 		otg_id = dwc3_meson_g12a_get_id(priv);
 		if (otg_id != priv->otg_phy_mode) {
 			if (dwc3_meson_g12a_otg_mode_set(priv, otg_id))